There are known various means for viewing the interior of a process vessel during a manufacturing or reaction phase. The simplest means is to provide a viewing window located in the wall of the vessel for visual observation of the activity within the vessel. Several of these viewing windows are disclosed in U.S. Pat. Nos. 2,744,487; 3,299,851; 3,837,226 and 4,245,566. A serious drawback to the use of these viewing windows is the possibility of failure or rupturing of these windows when used in a high pressure or high temperature system. Personnel using or in the vicinity of these window could be seriously injured if the windows fail to withstand the internal pressure generated within the reaction vessel. To correct this drawback, a safety glass viewing window was provided in U.S. Pat. No. 4,809,862 (Canty). Canty provided a novel safety viewing window that was substantially safer and more structurally sound for use in a high pressure-high temperature vessel.
To extend the safety of these type devices a viewing of the interior of high pressure process vessels through a remote location at a safe distance from the vessel is highly desirable. There are situations where explosion potential exists during the use of these vessels and optimum safety can be afforded by removing personnel from the area of the vessel location. At the same time window viewing of the interior activity of a reaction (or other) vessel can only provide instant viewing information. For example, if it was desired to play back a foaming operation or reaction process to determine color changes, reaction levels or densities or other relevant factors, instant viewing through a window would not provide such an opportunity. It is highly desirable to provide a system for viewing the interior of such vessels at a remote location by the use of a viewing camera that can not only provide instant viewing but can also allow recording of data for later study or by the use of appropriate computer programs and digital information fully analyze the activity taking place or that earlier took place. A camera viewing could afford substantial advantages in addition to safety than are presently provided by viewing windows for direct personal viewing. There have been some attempts in both (A) standard viewing (not high temperature or high pressure vessels) and (B) hazardous area viewing to utilize cameras for this purpose.
(A) In standard viewing in a high pressure/high temperature system, users have been limited to makeshift methods. Generally, to view the interior of a vessel at a remote location, the user would have to mount a CCD or CCTV Camera onto an existing sightglass window. Any suitable camera may be used. They would then encounter some or all of the following problems that would render the system ineffective: PA1 (B) Hazardous area viewing to date in industry has been performed by using a nitrogen-purged housing. The nitrogen purge is provided to eliminate and dilute hazardous vapors and prevent them from exploding. The nitrogen-purged housing is made of thin gauge metal with a window that the CCD Camera sees through. The limiting factors in the design are: PA1 (a) Fused glass to metal sealed front plano-plano lens. Hermetically sealed does not allow any vapors to enter. PA1 (b) O-ring sealed fuseview lens holder to metal (or plastic) house. Along with a rear O-ring threaded seal cap provides the strength and integrity needed to prevent an internal explosion from breaking the housing apart and the threading keeps the flames from propagating out, thereby making unit explosion-proof without purging. The O-ring sealed housing makes it also Nema 4 weatherproof. The fuseview (fused glass to metal sealed lens) will withstand the internal explosion along with maintaining a hermetic, gasketless seal. An O-ring is a self-energizing seal (meaning no torque or force is required to "seat" the O-ring) that has a circular cross section and is made of an elastomeric material (an elastomer material is one that can be compressed and then released and after it is released it will return to its original shape). The O-ring groove used in this invention is a standard design. Nema 4 is an area classification for electrical enclosures. A Nema 4 enclosure is suitable for outdoor use and areas where it may be washed down with water. Nema is a standard electric code that has numerals to designate set electrical standards. PA1 (c) Focusing of the vision system CCD Camera or other style imaging device can be performed external to the housing through the rear focusing screw. This threaded focusing screw pushes continually on the camera since the camera is spring mounted in the front on slide bearings. This concept is unique since most cameras are focused by moving the lens package back and forth. In the present invention it is extremely important to maintain the lens distance as close to the front fused lens as possible in order to maximize the viewing angle. If the lens retracts the view angle retracts and has a potential to interfere with the wall of the fuseview (or pressure vessel wall). This eliminates the need to open the housing of the present invention which could cause an accident, explosion or allow vapors to attack the unit. PA1 (d) The spring-loaded bearing mount CCD Camera allows a servo motor, drive motor, hydraulic operator or air operation to move the lens the required distance for focusing remotely instead of using the focusing screw. PA1 (e) The front alignment plate carries the slide bearing mount. It also serves as a mounting plate for the lens cartridge on the explosion-proof camera. This plate is mounted by two screws in slotted holes. By loosening the screws the CCD Camera (or any other imaging device) can be rotated relative to the view object. This creates the proper image orientation on the monitoring screen. This plate also keeps the lens assembly at the optimum fixed position. PA1 (f) A telephoto lens that is manually or electrically driven external to the housing and can be used keeping the integrity of the housing intact. One can attach the center focusing lens to the CCD while fixing the remaining lens to the alignment plate or fused lens assembly. To focus a telephoto lens a center (lens located in the middle) needs to be moved relative to the lens assembly infront and the lens assembly behind. In a standard design it is easy to accomplish this. Anyone using this system can adjust the lens by rotating the body. In the present invention, the adjusting lens is fixed to the camera body. This moves this lens with the camera and keeps the other stationary. A bracket spanning the camera can be used if zoom lens is used once it is focused.
(1) The sightglass and CCD lens would become dirty due to dirt external to the vessel. PA2 (2) The process fluid or vapors would leak out or flow out due to a sightglass breaking or leaking. This would then destroy the electronics making the system worthless. PA2 (3) Reflection from room lighting would cause the vessel view to disappear. PA2 (1) Purging is a continuous cost of operation. PA2 (2) Instrumenting the purge gas and piping the purge gas is very expensive and limits the locations where the camera can be mounted. PA2 (3) The gasketed window that the CCD Camera looks through is fragile and subject to breakage. Not only is there maintenance and replacement cost but there is also a major safety hazard created if the purge controls do not operate properly. PA2 (4) Hazardous area viewing of a high pressure area has not been attempted due to the combination of problems from 1, 2 and 3 above. One would currently have to use a purge camera housing on a sightglass and suffer from all of the problems mentioned above.
The structures of a camera device on a reaction vessel could easily become corroded and could fail. Uneven glass loading due to uneven bolt or gasket stresses can cause cracking and leakage. Also, corrosive chemicals during extended usage could cause failure of these mounting structures or failure of the camera being used. The camera systems of the prior art are cumbersome, oversized and in many instances tend to reflect light and cause image distortion. In addition, focusing and manipulating of the camera to provide optimum usage has been difficult when using prior art devices. Therefore, while some degree of improvement is provided by camera viewing heretofore used, none of these systems provide an adequate system for reliable and extended usage.